Apparatus for protection of in situ combustion wells



Aug. 24, 1965 H. w. PARKER APPARATUS FOR PROTECTION OF IN SITUCOMBUSTION WELLS Filed Feb. 9, 1962 INVENTOR. H. W. PA R K E R UnitedStates Patent 3,202,219 APPARATUS FOR PROTECTION OF IN SITU COMBUSTIDNWELLS Harry W. Parker, Bartlesviile, Okla, assignor to PhillipsPetroleum Company, a corporation of Delaware Filed Feb. 9, 1962, Ser.No. 172,330 3 Claims. (Cl. 166-53) This invent-ion relates to anapparatus for protection of production wells utilized in producingcarbonaceous strata by in situ combustion.

The use of in situ combustion to produce hydrocar- :"bons fromoil-containing strata is, becoming more prevalent in the petroleumindustry, In effecting this type of production, the stratum to :beproduced is ignited around a well bore penetrating same and theresulting combustion zone is moved into the stratum toward one or moreoffset wells therein. In some applications, air or othercombustion-supporting gas is injected thru the offset wells and thru thestratum to the combustion zone which is caused to move toward the offsetwells inversely to the [flow of air. In this technique of operation, thewell around which the combustion is initiated also functions as aproduction well. Other applications of the in situ comlbustion processinject-air thru the wellaround which combustion is initiated so as todrive the combustion Zone by direct drive toward the offset wells. Inthis manner, the offset well or wells become production wells.

In either case (direct or inverse drive of the combustion front) hotproduced gases flow into the production well, from the beginning ofproduction when utilizing inverse drive, and somewhat later in theproduction operation when utilizing direct drive of the combustion zone.The produced gases, particularly during inverse drive reach temperaturesas high as 2,000" P. and are usually at least 800 in temperature. Suchhigh temperatures have a deleterious effect upon production wellequipment and sometimes fuse the rock around the production well so asto reduce the permeability of the borehole wall sufficiently tointerfere with production.

It is also desirable to maintain the production well temperature withinreasonable limits because of the fact that a certain proportion of theinjected air appears in the production borehole 'by bypassing thecombustion zone and the presence of the oxygen in the production well inadmixture with hot produced hydrocarbons results in combusti-on of thehydrocarbon which not only destroys valuable production but .alsoincreases the temperature in the well. This invention is concerned witha method and apparatus for effectively controlling the production welltemperature within limits which avoid damage to the well equipment andassure preservation of the produced hydrocarbons.

Accordingly, it is an object of the invention to provide an apparatusfor controlling production well temperatures. Another object of theinvention is to provide an apparatus for controlling production welltemperatures utilizing coolant produced in the process. A further objectis to protect well equipment during in situ combustion production andpreserve produced hydrocarbons. Other objects of the invention willbecome apparent upon consideration of the accompanying disclosure.

A broad aspect of the invention comprises an apparatus for cooling thehot effluent from a production well being utilized in an in situcombustion process to condense rnost of the produced hydrocarbons,separating the condensed liquid from the effluent, and passing theuncondensed gases into the production well within the stratum beingproduced so as to mix the cooled gases with the hot produced gases andreduce the temperature thereof to 3,2612% Patented Aug. 24, 1965 ICC arange which does not deleteriously affect the well equipment and whichprevents combustion of hydrocarbons withibypassed oxygen as these gasesenter the well. The uncondensed gases from the process consistprincipally of CO and nitrogen, the major portion of the producedhydrocarbons having been condensed from the efiiuent by the quenchingand/or cooling step applied to the produced gases.

The amount or rate of recycle of uncondensed gases from the cooled welleflluent depends upon the rate of production of hot gases in theproduction well and the temperature level of these gases entering thewell. The temperature of the produced gases, preferably at a locationwithin the lower end of the tubin stringconducting the produced gases tothe well head, is sensed and the sensed temperature is utilized tocontrol the rate of flow of cool gas into the well so as to maintain thetemperature at the sensing point Within a safe range, the broad rangebeing 250-750 F, .and, preferably, 500 to 650? F.

A more complete understand-ing of the invention may be had by referenceto the accompanying schematic drawing which is an elevation in partialsection illustrating a preferred arrangement of apparatus forcontrolling the temperature in the production well.

Referring to the drawing. a carbonaceous stratum 10 is penetrated by aproduction well 12 and an offset well 14. Well 12 is provided with acasing .1 6and a tubing string 18 extending from within stratum 10,preferably, from a lower level therein, thru the well head. Well 14 isalso provided with a casing 29 and a tubing string 22 for injection ofair or other combustion-supporting gas from line in which is positioneda blower or compressor 26.

A production or eifluent line 28 connectstubin'g. string 18 with aseparator 30. A condenser or other cooling means 32 is positioned inline 28. Cooler 3 2 may comprise a quench vessel into which is injecteda water spray or other liquid or gaseous coolant or it may comprise anindirect heat exchanger. The essential function of this piece ofequipment is to reduce the temperature of the effluent passing therethruto a level which condenses most of the hydrocarbon material in theeffluent so that the liquid hydrocarbon may be withdrawn from separator30 via line 34-. Condensed water is vented. th-ru line 3 6 anduncondensed gases are vented thru line 338.

The recycle system comprises conduit 40, surge tank 42, and conduit 44which connects with the annulus of the Well thru connector 46. Acompressor 48 in line 40 maintains a relatively constant pressure insurge tank 42, drawing gas from exhaust line 38.

A motor valve 50 in conduit 44 controls the flow rate therein and iscontrolled or regulated by a servo-system 52 which is operativelyconnected therewith. A thermocouple or other temperature sensing means54 positioned in the well adjacent the stratum, such .as in the lowerend of tubing 18, is connected by means of line 56 with theservo-system. An alternative but less effective location of thethermocouple is at 58 in line 28. The servo-system may be eitherelectric or pneumatic, both systems be ing in conventional use forreceiving a signal in response to a sensed temperature and emitting asignal which is used to control a motor valve. The motor valve may beeither pneumatically or electric-ally operated as both types arecommercially available.

:In operation, a combustion zone 60 is being moved thru the stratumlying between Wells 12 and 14 by air injected thru line 24- and tubingstring 22. llf the process is a direct drive process, the combustionzone is initiated around well 14 so that the combustion zone is movedtoward well 12. In the event an inverse drive is being utilized, thestratum is ignited around well 12 and the resulting combustion zone isbeing moved toward well 3 14 inversely to the -flow of .air thru thestratum. In either event hot produced gases are flowing from thecombustion zone into well 12 and into the lower end of tubing string 18as shown by the arrows 62. The hot gases pass thru the tubing 18 andline 28 thru cooler .and condenser 32 to separator 30. The eflluent iscooled to a temperature below about 200, the temperature of coolingdepending upon the type of hydrocarbons being produced. Cooleduncondensed gases are recycled from line 38 thru line 40, compressor 48,surge tank 42 and conduit 44 under the control of valve 50 into the wellannulus which leads to the lower end of tubing 18. This recycling ofcooled gas passes down the annulus as shown by arrows 64 and causesmixing of the cooled gas with the produced gases and tempering of thelatter so that the sensed temperature at 54 is maintained within therange of 250 to 750 F. and preferably, 500 to 650 F.

7 It is desirable to maintain the temperature of the eiiluent gasintubing string 18 and line 28 at a sufiiciently high temperature sothat substantially all of the produced hydrocarbons flow out of the wellin vapor form so that pumping equipment in the well is not required.Another advantage in maintaining the effluent gas temperature relativelyhigh, 'but below temperatures which prevent combustion with bypassedoxygen and damage to the production well and its equipment, lies inmaintaining minimum volume of gas (measured at standard temperature andpressure) passing thru the production line. If more recycled gas isutilized in order to maintain low temperature in the effluent line, thisimposes additional volume requirements in the sepanation equipment.Hence, it is advantageous to use as small a volume of temperaturecontrolled gas as possible and still maintain the temperature below asafe level.

Thus it can be seen that the process of the invention utilizes readilyavailable gas in line 38 at suitable temperature for cooling in theproduction well. This recycled gas is principally nitrogen and CO and isnondeleterious tothe'equipmentand in the produced gases.

Certain modifications of the invention will become apparent to thoseskilled in the art and the illustrative details disclosed are not to beconstrued as imposing unnecessary limitations on the invention.

I claim? '1. Apparatus comprising in combination a tubing string in aproduction rwell penetrating a combustible carbonaceous stratum, saidstring extending thru the Well head at least to the level of saidstratum; an effluent line connected with said tubing string at the wellhead; cooling means in said efiluent line for liquifying hydrocarbonspassed therethru; separation means in said efiluent line for separatingcondensed liquids from uncondensed gases, including separate outlets forwater, oil, and uncondensed gases; conduit means connecting the separateoutlet for uncondensed gases of said separation means with the well borewith-in said stratum having a compressor therein for passing uncondensedgases from said separation means into hot produced gases passing fromsaid stratum to the lower end of said tubing string; flow control meansin said conduit; temperature sensing means for sensing the temperatureof efiluent hot gases; and means for regulating said flow control meansin response to the sensed temperature so as to control saidtempeuature'wit-hin a desired range.

' 2. The apparatus of claim -1 wherein said temperature sensing means isin said Well adjacent said stratum.

3. The apparatus of claim .1 wherein said temperature sensing means isin said efiluent line.

References Cited by the Examiner UNITED STATES PATENTS 2,630,307 3/53'Martin l66l1 2,853,136 9/58 -Moore et al. l66l-'l 2,969,226 1/ 61Huntington 166-11 X 3,013,609 12/61 Ten Brink 166-39 FOREIGN PATENTS1,223,078 6/60 France.

1. APPARATUS COMPRISING IN COMBINATION A TUBING STRING ING A PRODUCTIONWELL PENETRATING A COMBUSTIBLE CARBONACEOUS STRATUM, SAID STRINGEXTENDING THRU THE WELL HEAD AT LEAST TO THE LEVEL OF SAID STRATUM; ANEFFLUENT LINE CONNECTED WITH SAID TUBING STRING AST THE WELL HEAD;COOLING MEANS IN SAID EFFLUENT LINE FOR LIQUIFYING HYDROCARBONS PASSEDTHERETHRU; SEPARATION MEANS IN SAID EFFLUENT LINE FOR SEPARATINGCONDENSED LIQUIDS FROM UNCONDENSED GASES, INCLUDING SEPARATE OUTLETS FORWATER, OIL, AND UNCONDENSED GASES; CONDUIT MEANS CONNECTING THE SEPARATEOUTLET FOR UNCONDENSED GASES OF SAID SEPARATION MEANS WITH THE WELL BOREWITHIN SAIDSTRATUM HAVINGA COMPRESSOR THEREIN FOR PASSING UNCONDENSEDGASES FROM SAID SEPARATION MEANS INTO HOT PRODUCED GASES PASSING FROMSAID STRATUM TO THE LOWER END OF SAID TUBING STRING; FLOW CONTROL MEANSIN SAID CONDUIT; TEMPERATURE SENSING MEANS FOR SENSING THE TEMPERATUREOF EFFLUENT HOT GASES; AND MEANS FOR REGULATING SAID FLOW CONTROL MEANSIN RESPONSE TO THE SENSED TEMPERASTURE SO AS TO CONTROL SAID TEMPERATUREWITHIN A DESIRED RANGE.